This invention relates to a side wall clamp for secureing downhole tools in a cased or uncased bore hole. The clamp of this invention has particular utility when employed in conjunction with tools which are suspended on a wireline but also can be used in conjunction with tools carried by a string of drill pipe.
In the drilling of bore holes for exploration or production, it is frequently desirable to position various kinds of tools within the bore hole for obtaining measurements such as seismatic movements, gavitational forces, and the like, or for the performance of operations such as side wall coring or bore hole perforation. During such measurements or operations, it is frequently desired to firmly clamp or support the downhole tool in contact with the side wall of the bore hole or casing to prevent both vertical and lateral motion of the tool during the measurement or operation being conducted.
Various mechanical arrangements have been proposed heretofor such as inflatable packers or flexible strips or arms which can be mechanically actuated to engage the wall of the bore hole or casing and thus firmly support a tool in a fixed position. Defects in the prior devices are that they are subject to operational failure which may leave the tool in locked position within the bore hole with the result that it must be abandoned, destroyed, or only recovered by expenditure of great time and effort.
It is accordingly an object of the present invention to provide a side wall clamp for downhole tools which automatically releases the tool in response to slight upward movement of the wireline or drill string regardless of whether or not the clamp actuation mechanism is operative, thus providing a fail-safe operation.
A further object is to provide a clamping mechanism which in normal operation may be utilized sequentially (1) to clamp a tool at one location, (2) to be released, and (3) to again be actuated to clamp the tool at a second location without removal of the tool from the bore hole.